In steam turbines, leading edges of rotating blades may be exposed to water droplets, which make them prone to impact erosion, especially when the blade is made of materials such as composites. For this reason it is known to cover edges with material to increase erosion resistance. For example, U.S. Pat. No. 7,896,221 B2 discusses a manufacturing method that provides a portion of a blade aerofoil with increased erosion resistance. This is achieved by the use of titanium elements and a beta-stabilizing material. The titanium elements and the beta-stabilizing material are assembled such that the beta-stabilizing material is adjacent to the titanium elements. When heated the beta-stabilizing material diffuses into an adjacent portion of the titanium elements causing the adjacent portion of the one or more elements to have a beta microstructure which provides an increased erosion resistance. This solution requires the assembly of multiple elements in order to from an erosion resistance blade edge.
U.S. Pat. No. 5,782,607 discusses a further method that involves using replaceable ceramic insert that forms part of a protective sheath of a leading edge of a propeller blade providing a protective sheath. In order to facilitate maintenance and repair of the protective sheath, the sheath is held in place by a securing means such as adhesive, a screw or a pin.
In particularly for turbines blades that have edges curved in the circumferential direction, these solutions require the edge sheaths to be made of numerous smaller pieces bonded together.